A hybrid electric vehicle (HEV), an electric vehicle (EV), and the like use a assembled battery (battery system) made by connecting, in series, multiple cell groups including multiple single battery cells of secondary batteries connected in series or connecting multiple cell groups in series and parallel in order to ensure a desired high voltage. In such an assembled battery, for calculating residual capacity, protecting and managing each single battery cell, a cell controller, which measures a cell voltage (a voltage between terminals of a single battery cell) and performs balancing discharge for balancing of the state of Charge (SOC) and more specifically for balancing the residual capacity, is provided in a monitoring device of the assembled battery to manage the assembled battery (see PTL 1). This cell controller includes multiple integrated circuits (cell controller ICs) to manage multiple cell groups explained above.
An integrated circuit disclosed in PTL 1 includes a voltage detection circuit constituted by a differential amplifier and an analog digital conversion device, and measures a cell voltage by using this voltage detection circuit. In addition, by causing the voltage detection circuit to measure the voltage of an already-known reference power source, a diagnosis can be done to find as to whether the differential amplifier and the analog digital conversion device are operating normally.